Insertion of wire rips in can closures and apparatus therefor



Sept. 3, 1940.

INSERTION 0F WIRE RIPS IN CAN CLfJSURES AND APPARATUS THEREFOR FiledFeb. 24; 1938 4 Sheets-Sheet 1 go 55 I gmvkxfixw mvENTok P: rse Bonus?P. BOGNER 2,213,427

Sept. 3, 1940. P BQGNER 2,213,427

INSERTION 0F WIRE RIPS IN CAN CLOSURES AND APPARATUS THEREFOR Filed Feb.24, 1938 4 Sheets-Sheet 2 INVENTOR PETER Boa/v54? ATTORNEY:

Sept. 3, 1940.

P. BOGNER INSERTION OF WIRE RIPS IN CAN CLOSURES AND APPARATUS THEREFORFiled Feb. 24, 1958 4 Sheets-Sheet 3 I NVEN R PETER BOGNER WMM HTTORNEYSSept. 3, 1940.

P. BOGNER 2,213,427

INSERTION 0F WIRE RIPS IN CAN CLOSURES AND APPARATUS THEREFOR Filed Feb.24, 1958 4 Sheets-Sheet 4 l N V E N TOR PETER BOGNER ATTORNEXS PatentedSept. 3, 1940 UNITED STATES PATENT OFFICE INSERTION OF WIRE RIPS IN CANCLO- SURES AND APPARATUS THEREFOR British company Application February24, 1938, Serial No. 192,262

' In Great Britain March 23, 1937 8 Claims.

This invention consists in improvements in or relating to the insertionof wire rips in can closures and apparatus therefor.

The conventional can closure includes a central depression to fit withinthe mouth of the can body and a marginal flange which is intended to beinterfolded (as by a doubleor multiple-seaming operation) with anout-turned flange at the end of the can body so that the marginal flangeof the closure lies outside and is pressed to embrace the outer wall ofthe can body.

It has been proposed to include in the conventional can closure anopening device comprising a wire which is housed within the pressedcircumierential portion of the closure with an end protruding throughthe closure to the outside thereof. (Such opening wires are commonlytermed rip wires and as such will be referred to hereinafter.) Theconventional seamed closures provided with rip wire openers are intendedto be opened by inserting the protruding end of the rip wire into a keyand then winding up the wire upon the key by rolling the key around thecan so causing the rip wire to cut through the wall of the end closure.The opening of cans in this Way is not always easy and is not alwaysconvenient since opening keys are easily misplaced. The presentinvention is concerned with the insertion of rip wires into an improvedform of end closure which is such that opening of the closure may beefiected without the employment of a key or may be effected more readilythan with the conventional closures.

More particularly the present invention is concerned with a method andapparatus for inserting a rip wire into a can closure of the form havinga central depression to fit within the mouth of the can to be closed anda marginal portion constituting a flange for interfolding with the canbody, with the material of the closure continued outwardly from thedepression in the form of a narrow shoulder reaching to awire-supporting wall which extends to the marginal flange and upon whicha rip wire is intended to be held inside the closure, and having anopening to the outside of the closure through which the rip wire maypass to provide a purchase for ripping the closure open. Can closures ofthe aforesaid form constitute the subject-matter of my co -pendingUnited States application Serial No. 191,230, filed February 18, 1938.

Insertion of rip wires into the conventional closures has been efiectedby hand-threading. Can closures are producible at the rate of betweenone to two hundred a minute by a single ridge, a presser to hold theclosure in engagement machine but manual insertion of rip wires at thesame rate requires several operators and, moreover, the exact tensioningand positioning of the rip wire is not precisely repeatable with manualinsertion. Insertion of rip wires by hand is therefore undesirable andraises the cost of production to an extent disproportionate with thebenefits obtained. The primary object of the present invention is toprovide a method for inserting the rip Wires into can closures of theform dem scribed by mechanical means whereby the threaded closure canrapidly be produced to a desired standard.

The invention accordingly comprises a method of inserting a rip wireinto a can closure of the form described consisting in holding theclosure (before its application to the can) on a body member which fitsand closes the open side of the hollow ridge and then pushing the ripwire in endwise into the space within the ridge. 20

The rip wire may be pushed in endwise from the outer side of the closurethrough an opening at the end of the ridge. Preferably the wire isinserted into the ridge insubstantial alignment therewith.

The present invention is applicable to can closures of the formdescribed whether the area of the closure which is to be removed iscircular, oval or substantially rectangular inshape. In the latter case,the ridge should extend in an arcuate course at the corners of the areato facilitate advancement of, the rip wire around the corners.- In thecase when the ridgeextends in an arcuate path around the area to beremoved, for example about a circular or oval area; insertion of the ripwire should preferably be effected by thrusting it endwise in adirection substantially tangential to the ridge at the point of entry ofthe wire thereto. v The invention includes apparatus for threading a ripwire into a can closure oithe form described comprising in combination abase-member to fit and close the open side of the hollow with thebase-member, a guide-member to direct 5 or driving between thebase-member and the walls of the ridge.

Other objects of the invention are to provide positive location of theclosures with respect to the threading device and tensioning of the ripwire within the ridge after threading.

Further objects and advantages of the invention will appear from thefollowing description taken in conjunction with the accompanyingdrawings which illustrate by way of example one form of apparatus forcarrying the invention into effect.

Referring to the drawings:

Figure 1 is a perspective view to an exaggerated scale of the outside ofa circular end closure of the form referred to hereinabove in which thefront half of the closure has been broken away to show, in section, theconvolutions of the closure;

Figure 2 is a plan View to an enlarged scale of a jig for supporting theclosure-member during insertion of the rip-wire;

Figure 3 is a sectional elevation of the jig of Figure 2 taken on theline 33 thereof looking in the direction of the arrows;

Figure 4 is a sectional elevation similar to Figure 3 but to a largerscale showing a closure in position upon the jig, the central portionsof the closure and jig being broken away;

Figure 5 is a diagrammatic layout of the complete apparatus includingtwo jig tables and indicating the supply of end-closures to and thetake-off from the said tables;

Figure 6 is a perspective view of a jig table and associatedwire-inserting, wire-bending and wire-threading devices;

Figure '7 is a plan view of an end-closure in position upon a jigshowing the action of the wire-bending device;

Figure 8 is a side elevation of the bending device looking in thedirection of the arrow 8 oi Figure 7; and

Figure 9 is a fragmentary sectional elevation to a greatly enlargedscale of a modified form of ig.

Referring first to Figure 1 of the accompanying drawings the end-closureis of the form which constitutes the subject-matter of my co-pendingUnited States Patent application Serial No. 191,230, and comprises adished central portion surrounded by a crimped flange l2 which isbounded by an upstanding wall I3. The edge of the closure-memberis'constituted by a marginal flange I l which is curled over at l5around its periphery. A ridge I6 is upset within the area of and aroundthe marginal flange [4 in the opposite direction to the depressedcentral portion II to provide a space I! in the underside of the flange.The ridge is spaced somewhat from the upper edge of the wall l3 so as todivide ofi a portion of the flange I4 as a narrow inner shoulder I8 andterminates in a gap l9 where the metal of the flange I4 is not upset.Each end of the ridge is pierced with a hole, at 25] and 2|, whichestablishes communication from outside the closure to the space I!within the ridge. The holes 20 and 2| are located close to the apex ofthe ridge it so that the lower portions of the ends of the ridge areclosed by a lip of metal, as shown at 22.

The ridge I5 is intended to house a rip-wire opener within the space Has indicated at 23 in Figure 4, so that the rip-wire extends around theclosure with at least one of its ends protruding to the outside of theclosure through the holes 20 or 2!. The protruding end of the wire isintended to be such as to permit a purchase to be obtained for rippingthe closure open and to this end may be looped or may be provided with across-bar handle. The other end of the wire may be also brought throughthe end of the ridge via the other hole and solder spotted onto the wireat its point of emergence to anchor it in position. Alternatively, thisend of the wire may be anchored by deforming the metal of the end of theridge 16.

To obviate any tendency for the rip-Wire 23 to come away from theinterior of the ridge [6 it is upset with a non-divergent, substantiallycylindrical inner wall 24 which is joined to a curved outer wall 25. Bythe provision of the straight or cylindrical inner wall 24 the rip-wirecan be tightened in the space I! to bear upon the Wall 24 and heldthereon under tension by frictional engagement of the Wire with thewall. The walls 24 and 25 join substantially at a right angle (asindicated at 26) and the upsetting of the ridge is is preferablyeifected in such a manner that the metal of the ridge is reduced inthickness at the line of joining of the two walls to provide a line ofweakness in the ridge to facilitate ripping of the metal by the rip-wire23.

Insertion of rip-wires into closures of the form described isaccomplished in accordance with the present invention by positioning theclosure upon a jig which is such as to interfit with and to close thespace ll and by then thrusting the wire in endwise through hole 20 or 2|around the space H until the wire emerges from the other hole.

Figure 5 shows the general scheme of the apparatus comprising a station21 at which end closures, as shown in Figure 1, are stacked and may befed by an operator at 28 to each of two jig tables 29 and 30. The jigtables 29 and 30 rotate about vertical axes 3| and 32 respectively in astep-by-step fashion, in opposite directions, and each table carriesthree jigs (indicated by the general reference 33) which are brought inturn to jig-loading stations 34, wire-threading, bending and shearingstations 35 and jig-unloading stations 36. When the end-closures arriveat the stations 36 they each contain a ripwire Within the space H, thewire having been bent at its ends and tensioned within the ridge as willbe described hereinafter. The closures then pass via conveyor lines 31to a solderingstation 38 and may thereafter have a latex compoundapplied to the underside of the marginal flanges at the station 39.

At the threading, bending and shearing stations 35 the apparatus isduplicated and comprises wire-supply reels 40, wire-straightening means4i, pairs of wire-feed rollers 42, 43 and 44, shears i5, threading andguiding blocks 46 and wireanchoring, tensioning and bending devices 47.

Figure 6 is a perspective view of the jig-table 30 with the associatedwire-inserting apparatus. An empty jig 33 is shown at the positioncorresponding to station 36 of Figure 5 (it being assumed that a wiredclosure has just been removed), an end-closure is shown in position forthreading on a jig at station 35 and an endclosure is shown in chainline in position upon the jig at station 34 ready to be brought to thethreading station 35 by movement of table 30 in the direction of thearrow.

As Will be seen more clearly from Figures 2, 3 and 4, the jigs comprisea base-member 33 having an upstanding circular abutment 38 surrounding acircular depression 39 within which fits the dished portion of theend-closure. A narrow rib 59 extends around the top of the abutment 36and terminates in ends 5|, 52 which define a gap corresponding to gap I9in the ridge I6. The rib 56 is spaced from the inner and outer sidewalls of the abutment 38 thereby providing narrow inner and outercircular shoulders 53 and 54 respectively, around the top of theabutment. As will appear from Figure 4 the shoulders. 53 and 54 and theside Walls of the rib 56 are shaped to conform with the shaping of theopen side of the ridge I6 of the endclosure. Thus, the narrow shoulder53 and its upward sweep to the inner side wall of the rib 56 correspondsin shape with the narrow shoulder I 3 inside the ridge I6 and its upwardsweep to the inner cylindrical wall 24 of the closure. Similarly, thenarrow shoulder 54 and its upward sweep to the outer wall of the rib 56corresponds with the curved shape of the underside of the marginalflange I4 and its sweep into the curved wall 25 of the ridge I6. Foreasy threading of the rip wire it is essential that the rib 66 shouldfit snugly and accurately within the open side of the ridge l6 so thatsubstantially no space existsv between the side walls of the rib and theside walls 24 and 25 of the ridge. As will be seen from Figure 4, therib 56 is so proportioned as just to penetrate into the space ll of theridge thereby leaving a free space between its upper face and the apexof the ridge. The ends EI and 52 of the ridge are chamfered as shown inFigure 3 of the drawings and the chamfered faces fit against the lippedportions 22 of the ends of the ridge. It

will be noticed that in the construction illustrated the rip-wire 23lies wholly above a plane containing the upper side of the marginalflange E4 of the end-closure and the holes 26 and EI, mentionedhereinabove as located towards the apex of the ridge, are positioned inthe same plane as the wire 23. The jigs 33 are secured to the jig table36 by means of screws 55 passing from the underside of the table and areeach provided with an inner depressed portion 56 of a shape whichcorresponds to the inner depression II of the end-closures.

Turning now to consider the threading-station 35 as illustrated inFigure 6, a pressure member 5? is mounted upon a piston 58 for Verticalsliding movement within a guide 59 (the actuating means for the pressernot being shown). The threading-block 46 is also carried upon a rod 36for vertical sliding movement within a guide 6!, the means for movingthe threadingblock also not being illustrated. The presser member 5? iscylindrical in shape and corresponds to the circular depressed area I Iof the end-closures. It is mounted Within the guide 59 so as to bebrought down exactly to fit within the depressed portion II of theend-closures to press the said portion into the inner depression 56 ofthe jig 33 when the jigs are brought to the threading station. At thetime during which the table 36 is moving to bring a freshly loaded jigbeneath the presser member 51, both the presser member and thethreading-block 46 are in the raised position to permit the jig andendclosure carried thereby to move to the threading station. Thethreading-block 46 is so located that when the jig table ceases to movethe threading-block may be brought down to lie within the gap I 9 of theridge I6. The underside of the threading-block 46 is grooved to providea semi-conical guiding tunnel 62 which tapers towards the opening 22 inthe ridge I6 of the. underlying closure. The axis of the semi-conicaltunnel is substantially tangential to the direction of the ridge l6. Thethreadingblock 46 carries a semi-circular lateral extension 63 whichextends in alignment with the axis of the guide tunnel 62 and in linewith the wire feed from the pairs of feeding rollers 42, 43 and 44.

The feeding rollers 42, 43 and 44 are geared together for rotation inpairs and are mounted for rotation in a supporting framework 64. R-tation of the feeding rollers 42, 43 and 44 is brought about from acounter-shaft 65 carrying inclined bevel gears 66 which mesh withinclined bevel gears 67 carried at the end of the upper roller of eachof the pairs of feeding rollers 42, 43 and 44. A clutch device (not .11-lustrated) is provided for actuating the countershaft 65 periodically sothat the feeding rollers are brought into operation to feed wire '68 tothe guiding extension 63 into the guide tunnel 62 as soon as thethreading-block 46 and the presser-member 51 have been brought down upona fresh end-closure. Continued rotation of the feeding rollers causesWire 68 to be advanced to the tapered end of theguide tunnel 62 directlyat the hole 26 in the end of the ridge I6. Upon furth r feeding movementof the rollers 42, 43

and 44 the wire 68 is thrust through the hole 213 and is caused toadvance within the space in the ridge I6 between the upper face of therib 56 of the jig and the apex of the, ridge, travelling therearounduntil the advancing end of the wire comes to the hole H at the other endof the ridge. The threading-block is formed with a. wire receivingpassage 69 which at this stage of the operations has its openingregistering with the hole 2!. The passage 69 is located close to theunderside of the block 46 and runs into it from the side face of theblock for a short distance turning then inwardly with a right angle bandto extend in a direction parallel with the side face of the block. Whenthe advancing end of the wire reaches the end of the ridge it is thrustthrough the passage 2| into the hole 69 and upon continued advancementthe end of the wire 66 is deflected by the hole 69 and is bent round tolie at right angles to the ridge l6.

The time during which the rollers 42, 43 and 44 are clutched-in forfeeding movement is such as to ensure the advancement of a completeripwire into the ridge I6 and to provide also for a short projection ofthe end of the Wire through hole 2i into the groove 69. When therip-wire has been inserted to the extent described rotation of thefeed-rollers is stopped by automatic de-clutching of the counter-shaft65.

In order to prevent the advancing end of the Wire 68 from dropping outof the extension 63 at the commencement of the feeding operation (duringwhich time a sheared end of the wire is being fed through the feedingrollers as Will be seen hereafter) but at the same time to permit theextension 63 to be raised without at the same time raising the wirewhich at the end of the insertion operation bridges the space betweenthe rollers 44 and the guide tunnel 62 the extension 63 is left openatits under side. When the threading-block 46 is in the operativeposition, however, the extension 63 overlies a plate I6 which isattached to the framework 64 so. as just to clear the marginal flange I4of the end-closure upon rotation of the table to bring a fresh jig tothe threading station.

Throughout the threading operation the threading-block 56 is locked downin engagement with the closure by suitable means which acts upon the rod66. At the end of the threading operation the lock on the rod 60 isreleased automatically at the same time as the wire-feed rollers ceaseto feed wire and the threadingblock 46 is then raised to permit thewire-bending and tensioning tool t? referred to hereinabove to be movedradially into the gap I9. When the threading block is raised the end ofthe wire 68 is pulled out of the hole 89 and is engaged by the lowerboundary of opening thereof so as to be bent sharply at the end of theridge to stand up at right-angles to the end closure, ready for the nextoperation.

The tool 41 includes a smooth, approximately half-round, parallel sidedbody-portion which terminates in a smooth nose member H. One side of thenose member 1| is cut away diagonalwise to provide a sloping edge 13 andthe other side of the nose member extends in alignment with the side ofthe body-portion and constitutes a wire-bending and wire-anchoring edgel2. As will be clearly seen from Figures 7 and 8 the nose member Htapers both in width and in thickness towards its front end. A shoulderl4 separates the nose member ll from the bodyportion and extends fromthe back-end of the sloping edge 73 across the width of the tool 41 in aslightly rearward direction. The tool t! is, in addition, provided witha lip 75 which overlies the edge 12 whilst the side of the tool isundercut between the edge 72 and the lip 75 to provide a recess alongthe side of the tool beneath the lip.

The tool 47 is advanced radially into the gap it, by suitable means notshown, on a level with the upper side of the marginal flange M of theend-closure and is held during advancement against lateral movement. Theadvancing tapered end of the nose-member "H slips beneath the wire 88where it extends between the rollers i and the hole 20 and the saidportion of the wire starts to ride-up the inclined face of thenose-member. At this time the end of the ripwire which protrudes fromthe hole 2! and stands up at right angles to the closure is held only bythe bend in the wire at the end of the ridge. When the other end of thewire com mences to ride up the slope H of the tool 4! the protruding endof the rip-wire tends to retract into the ridge [8 through hole 2| andthe bend in end of the rip-wire is thereby slightly opened. Furtherslight advancement of the tool 41 brings the bending edge 12 intocontact with the protruding end of the rip-wire which is thereupon bentsharply inwards against the end of the ridge l6 and thereby anchoredagainst further retraction into the ridge Hi. In the continuedadvancement of the tool 41 the anchored and bent-over end of therip-wire rides along the bending edge i2 inside the recess beneath thelip 75 and is thus tucked away so as to be clear of engagement with theportion of the wire 68 which is at the same time riding up the slope ofthe nose-member TI. The other end of the rip-wire is also held aganstany substantial movement between the nip of the feeding rollers andcontinued advancement of the tool 4'! serves to tighten the rip-wireupon the inner cylindrical wall 2 of the hollow ridge I6 by bending thewire in an are over the nose-member H. Further advancement of the toolcauses the shoulder M to engage the rip-wire which upon forward movementof the tool kinks the wire abruptly at the point where it enters theridge through hole 20. The wire is kinked to an extent suflicient tohold the rip-wire under tension in the ridge when the tool is withdrawn.

After the wire 68 has been kinked in the manner described the shears areoperated to cut the wire 68 where it extends between the feed rollerpairs 43 and 44. The tool 47 is then retracted. The presser member 51 isthen raised, the table 3t] is rotated to bring the next jig loaded witha new closure to the threading station 35 whilst the wired cover ismoved round to the take-off station 36, the feed rollers beingmomentarily engaged to feed the end of the rip- Wire out of the rollers44.

The wire end-closures are passed from the take-01f stations 36 to thestation E38 where a spot of solder is applied to the ends of the ridgeit where the rip-wire emerges from the holes at and H. The holes 20 and2| are thereby closed and the wire positively held against release oftension in the ridge. The end closures then pass to station I39 for theapplication of a latex compound on the underside of the marginal flanges14 of the closures.

The wired end closures may thereafter be operated upon to form a loop inthe end of the wire where it emerges from the hole 20 and to engage theloop with the hook on the wire end which protrudes from the hole 2|. Theloop and hook can then be ironed down to lie flat in the gap 69. A1-teinatively, the end of the wire protruding from the hole 2t can be cutoil so as to provide a length of wire which lies across the gap and thecut end of the wire bent back and ironed down to lie within the gap orbent down the wall 13 and then bent a gain to lie across the depressedportion it. As a further alternative the end of the wire protruding fromthe hole 20 may have a crossbar handle attached to it and the wire bentdown the wall It and across to the depressed portion ll so that thehandle lies in the portion H.

In the next threading operation the presser member 5'! and thethreading-block 4t descend again upon the top of a fresh end closure.The feeding rollers 42, 43 and M are again rotated by clutching thecounter-shaft 56 to the driving means. To ensure that the sheared end ofthe wire 68 projecting from the feed rollers 43 is thrust forward inexactly the same line past the shears l5, during the momentaryengagement of the feed rollers to clear the wire end from the rollersit, a hollow conical guide it is secured to the framework fi l betweenthe pairs of feeding rollers 33 and 44 so as to lead the wire into thegrooved nip of the rollers M.- and thence to the extension 63 and theguiding tunnel 62.

In the modified form of jig which is shown to a greatly enlarged scalein Figure 9, the end-face or wire-guiding surface of the rib 58 isformed with a shallow arcuate groove 59a whilst the up per-edges of theside-walls of the rib are chamfer'ed at 5%. Such a configuration of theendface of the rib has been found useful as both assisting easyinsertion of the rip-wire and in providing for ready seating of theend-closure upon the jig.

I claim:

1. A method of inserting a rip-wire into a can closure of the formdescribed having the wire supporting wall forming part of a hollow ridgewith an open side which ridge has an end wall formed with an opening forthe passage of the rip wire consisting in holding the closure before itsapplication to the can on a body member which fits and closes the openside of the hollow ridge and then pushing the rip-wire in endwisethrough the said opening into the space within the ridge.

2. A method of inserting a rip-wire into a can closure as claimed inclaim 1 wherein the hollow ridge of the closure bounds a substantiallycircular area to be removed, comprising eilecting insertion of therip-wire by thrusting it endwise through the said opening in a directionsubstantially tangential to the ridge at the point of entry of the wirethereinto.

3. A method of inserting a rip-wire into a can closure of the formdescribed having the wire-supporting wall forming part of a hollow ridgewherein there is a gap with an opening to the outside of the closurefrom the hollow interior at each end of the ridge, consisting in holdingthe closure before its application to a can on a body member which fitsand closes the open side of the hollow ridge, thrusting the rip-wire inendwise, from the outer side of the closure, through one of the saidopenings into the hollow interior of the ridge and advancing therip-wire along the interior of the ridge by continued application of theendwise thrust to cause the end of the wire to emerge through the otherof the said openings to the outside of the closure.

4. A method of inserting a rip-wire into a can closure of the formdescribed, consisting in holding the closure before its application tothe can on a body member which fits against the closure so as to shutoff a hollow space between the marginal flange and the wire-supportingwall and then pushing the rip-wire in endwise into the said spacethrough an opening formed in a portion of the can closure bounding saidspace.

5. In apparatus for threading a rip-wire into a can closure of the formdescribed, the combination comprising a base member shaped to it againstthe closure to shut ofif a hollow space between the marginal flange andthe wire-supporting wall, means for holding the closure in engagementwith the base member, guiding means to direct the rip-wire endwise tothe said hollow space, a wire-feeder, means for mounting said wirefeederin position to advance the rip-wire endwise to the guiding means andthence into said hollow space, and means for bringing said wirefeederinto and out of operation.

6. Apparatus for threading a rip-wire into a can closure of the formdescribed having the wiresupporting wall forming part of a hollow ridgewith an open side, comprising in combination a gagement with thebase-member, means permitting relative movement between the base-memberand the presser to release the closure, a guidemember to direct therip-wire to the opening in the can closure, a wire-feeder to advance theripwire endwise via the guide-member through the said opening into thespace within the ridge, means for supporting said base-member, presserguide-member and wire-feeder, and means for operating the wire-feeder toadvance the ripwire.

7. In apparatus for threading a rip-wire into a can closure of the formdescribed having the wire-supporting wall forming part of a hollow ridgewith an open side, the combination comprising a base-member having anoutstanding rib which conforms to the course of the ridge in the canclosure, the said rib being such as to interfit with and to close theopen side of the ridge but and the apex of the ridge to receive thewire,

means for holding the closure in engagement with the base-member, aguide member for the rip-wire, means for supporting the guide-member inposition to direct the rip-wire endwise into said space through anopening in the can closure, a wire-feeder to advance the rip-wireendwise via the guide-member into said space, and means for operatingsaid wire-feeder to advance the ripwire.

8. In apparatus for threading a rip-wire into a can closure of the formdescribed havingthe wire-supporting wall forming part of a hollow ridgewith an open side and having a gap formed in the ridge, the combinationcomprising a jig having an outstanding rib which conforms to the courseof the ridge and is cut away to form a gap over a distance correspondingto the gap in the ridge, the said rib being such as to interfit with andto close the open side of the ridge but to provide a space between theface of the rib and the apex of the ridge to receive the wire,

means for holding the closure in engagement.

